There is no but that is going to take you from TTC to US/IOA directly. It is called the Lynx system, and is Orlando's public transit system. You can take it directly to SeaWorld though. I believe there have been reports of people taking it from TTC to SW and then taking a different bus, or the I Trolley, to US/IOA. But, those all involve transfers. The fare to SW is about $1.50 pp each way.
A towncar service would run you about $60, plus tip, from your resort directly to US/IOA parking lot. Economical? Nope, but it sure is handy and a great way to go.